Acoustical device



Aug. 1 1, 1942.

E. W. DAViS ACOUS Filed TICAL DEVICE 2 Sheets-Sheet NOV. 14, 1941 7 SPEAKER AMPLIFIER Aug. 11, 1942'. E. w. AWS 2,292,745.

AGQUS'IICALDEVIGE Filed Nov. 14, 1941 2 Sheets-Sheet 2 Patented Aug. 11, 1942 UNITED STATES PATENT OFFICE ACOUSTICAL DEVICE Ernest W. Davis, River Forest, Ill.

Application November 14, 1941, Serial No. 419,144

6 Claims.

My invention relates to acoustical devices in which a musical sound is amplified by means of a transmitter, an amplifier, and a loud speaker. The object of this invention is to provide a device of the class described in which the tone quality of the initial sound is improved during its transmission to the amplifier.

A more specificobject is to provide means for producing a sound effect, derived from a single sound, but having properties equivalent to a plurality of sounds, so as to provide a sound quality resembling a choral effect. A further object is to provide means for altering the tone characteristics in accordance with the choice of the performer. These and other objects will appear as the description proceeds.

In the drawings:

Figure 1 is a rear elevation of the exterior of the device;

Figure 2 is a sectional elevation, the section being taken on the line 2, 2, in Figure 1;

Figure 3 is a circuit diagram;

Figure 4 is a diagrammatic representation of the polyphase wave formation produced by this device; and

Figure 5 is an elevation of a modified form of the device.

The mouth piece 6 connects with an air tube 1, which conducts air to the air jet 8 arranged to discharge a stream of air across the sound opening 9, whereby vibrations are produced in the resonance tube In. The frequency of these vibrations may be altered at will by the performer, who is enabled to move the piston H towards the right or left, as desired, by means of the handle l2.

The sound. emitted through the sound opening 9 impinges on the transmitter l3, which converts sound waves into electrical waves. These electrical waves are amplified by the amplifier l4, and the resulting amplified, electrical waves are converted into sound waves by the loud speaker l5, which may be placed in any desired location. The volume of the loud speaker I5 is controlled by the adjustable rheostat I6. These sound amplifying devices are so well known that detailed descriptionwould be superfluous.

The novelty of this device concerns the soundreflecting surfaces ll, l8, and i9, which are provided by glass, porcelain, metal, or other substance capable of providing an 'efiicient soundreflecting surface. These sound-reflecting surfaces are preferably concave, and are inclined at various suitable angles as shown, so that sound waves propagated from the sound opening 9 in three different directions are all reflected and converged upon the transmitter l3. Thus the sound waves emitted through the sound opening 9 may travel in three separate sound paths as indicated by the dotted lines 20, 20, 2|, 2|, and 22, 22, before they reach the transmitter I3.

The transmitter l3, and reflecting surfaces I1, 3, and ID are positioned to provide sound paths 20, 2|, and 22 of unequal length. This is done for a particular purpose which will be described hereinafter. In the embodiment of the invention as herein shown, this provision of unequal sound paths is accomplished by positioning the r fleeting surfaces |'I, |8, andl9, at enequal distances from the transmitter l3. Sound paths of un equal length might also be provided by positioning the reflecting surfaces at equal distances from the transmitter I3, and by positioning the sound source at a location that is not equidistant from the reflecting surfaces ll, l8, and I9. The arrangement herein shown is the preferred construction, but any arrangement of the various elements that provides sound paths of unequal length will accomplish the purpose of this invention.

The purpose of providing sound paths of unequal length will now be described. A sound wave emitted through the sound opening 9, and travelling along the three separate sound paths 20, 2|, and 22, is virtually the same as three sound waves when the sound enters the transmitter l3. These three waves have the same frequency and the same wave pattern, but the sound wave delivered along sound path 2| will reach the transmitter 3, a fraction of a second later than the sound wave delivered along the sound path 20, because of the limited velocity of sound and the difference in length of the sound paths. This causes the wave of sound path 2| to be displaced in time and therefore retarded with reference to the wave of sound path 20 when both waves reach the transmitter l3. In other words, the two waves are out of phase with reference to each other. In the same manner the sound wave of sound path 22 will be out of phase with reference to the sound wave of path 2|, and the combined action of these effects is the production of a polyphase wave pattern.

This polyphase wave pattern is illustrated diagrammatically in Figure 4. The sound wave of sound path 29 is indicated by the full line 23; the sound wave of sound path 2| is indicated by the dotted line 24; and the sound wave of sound path 22 is indicated by the broken line 25. Sound waves are also reflected from the walls 26 and 21, thereby combining to form a complicated and intricate Wave pattern which is diflicult to illustrate completely, but which is pleasing to the ear. This wave pattern is virtually a plurality of sounds, all having the same frequency, so that the composite sound resem-v bles a choral effect with the various component sounds in perfect unison. Referring to Figure 2, it will be noted that the sound waves are reflected through relatively short distances, so that no perceptible echo is produced.

The transmitter I3 is secured to the rotatable shaft 23, which may be rotated manually by means of the knob 29, Figure 1. so as to swing the transmitter l3 to various selected positions. This alters the relative effective amplitude of the component, reflected waves, so that various tone qualities may be selectively obtained in accordance with the hoice of the performer. openings 30, 30, Figure 2, permit the escape of air that is blown in through the mouthpiece 6.

In the modification of the device illustrated in Figure 5, the sound emitter 3| is constructed in the shape of a horn with a sound receiving end 32 for receiving sounds to be amplified and a sound emitting end 33 for emitting the sounds received at the receiving end. The receiving end 32 is adapted for receiving sounds from anyone of various musical instruments played in close proximity thereto, or, if desired, a singer may sing into the receiving end.

The sound emitter 3| is arranged to transmit sound waves to the three spherically concave reflectors 34, 35, and 36, each of which is inclined to reflect, sound waves in focused concentration on the transmitter 31. These sound waves are picked up by the transmitter as separate waves out of phase with each other as hereinbefore explained, so as to provide a composite sound wave having a polyphase wave pattern. The transmitter 31 converts this wave pattern into electrical waves, which are amplified by the amplifier 38, and then converted into sound waves by the loud speaker 39.

If desired this device may be modified by increasing or decreasing the number of reflecting surfaces. Also, the sound producer illustrated in Figures 1 and 2 could be replaced with some other kind of a sound producer. These and many other modifications could be made without departing from the spirit of the invention.

I claim:

1. Anvacoustical device comprising an enclosure having sound reflecting walls; a resonance tube within said enclosure, said resonance tube having a sound opening therein; an air Jet arranged to discharge a stream of air across said sound opening whereby air vibrations are set up in said resonance tube; a mouthpiece exterior to said enclosure; a tubular portion connecting said mouth piece with said air jet; a movable piston within said resonance tube for regulating the frequency of said air vibrations; a manually operated movable member exterior to said enclosure; a connecting element connecting said manually operated member with said piston whereby said piston may be moved within said resonance tube by movement of said manually operated member; a transmitter within said enclosure, said transmitter being capable of converting said air vibrations into electrical waves; an amplifier for amplifying said electrical waves; and a loud speaker for converting said amplified electrical waves into sound waves.

2. An acoustical device comprising an enclosure having sound-reflecting walls; means for producing musical sound waves within said enclosure; a transmitter for converting said sound waves into electrical waves, said transmitter being enclosed within said enclosure; an amplifier for amplifying said electrical waves; a loud speaker for converting said amplified electrical waves into sound waves; a manually operated member outside said enclosure; whereby movement of said manually operated member changes the pitch of said sound waves; said sound-reflecting walls being located at un- The and means equal distances from said transmitter whereby the sound waves emitted by said sound producer are reflected to said transmitter in polyphase formation for the purpose set forth.

3. An acoustical device comprising a sound producer capable of producing musical sound waves; a transmitter for converting said sound waves into electrical waves; an amplifier for amplifying said electrical waves; a loud speaker for converting said amplified electrical waves into sound waves, and a plurality of sound-reflecting surfaces associated with said sound producer and arranged to reflect sound waves emitted by said sound producer, into said transmitter; said transmitter and said sound-reflecting surfaces being positioned to provide sound paths of unequal length whereby said emitted sound waves travelling along said sound paths are reflected into said transmitter in polyphase formation for the purpose set forth.

4. An acoustical devi comprising a sound producer capable of pi 'cing musical sound waves; a transmitter for nverting said sound waves into electrical waves; an amplifier for amplifying said electrical waves; a loud speaker for converting said amplified electrical waves into sound waves; a plurality of sound-reflecting surfaces associated with said sou; i producer and arranged to reflect sound wave: emitted by said sound producer, into said transmitter, said transmitter and said sound-reflecting surfaces being positioned to provide sound paths of unequal length whereby said emitted sound waves traveling along said sound paths are reflected into said transmitter in polyphase format. n; and means for manually altering the position of said transmitter relative to said sound reflecting surfaces, whereby the wave pattern transmitted by said transmitter may be selectively altered in accordance with the choice of the performer.

5. An acoustical device comprising a transmitter for converting sound waves into electrical waves; an amplifier for amplifying said electrical waves; a loud speaker for converting said amplified electrical waves into sound waves; and a plurality of concave reflecting surfaces positioned to receive musical sound waves emitted from a single location, said reflecting surfaces being inclined at various angles for reflecting said sound waves in converging concentration into said transmitter, and said transmitter and said reflecting surfaces being positioned to provide sound paths of unequal length whereby said emitted sound waves travelling along said sound paths are reflected into said transmitter in polyphase formation for the purpose set forth.

6. An acoustical device comprising a plurality of reflecting surfaces; a sound emitter associated with said reflecting surfaces; a transmitter for converting musical sound waves emitted by said sound emitter into electrical waves; an amplifier for amplifying said electrical waves; and a loud speaker for converting said amplified electrical waves into sound waves; said reflecting surfaces being inclined to reflect sound waves emitted by said sound emitter, into said transmitter, and said transmitter and said reflecting surfaces being positioned to provide sound paths of unequal length whereby said sound waves travelling along said sound paths are reflected into said transmitter in polyphase formation for the purpose set forth.

ERNEST W. DAVIS. 

